1. Field of the Invention
The invention relates to an electrical switch for indicating pressure change in a vehicle tire from a predetermined value, either above or below the predetermined value; the switch being normally closed when the predetermined desired tire pressure exists within the tire, and opening when the tire pressure is increased or reduced from the predetermined value, for actuating an induction or magnetically activated signaling system to provide a signal to the vehicle operator of the changed tire pressure condition.
The improved switch construction may activate an induction signal system such as shown in Brown U.S. Pat. No. 3,093,812, or in my copending application Ser. No. 567,533.
2. Description of the Prior Art
Many vehicle tire pressure signaling systems have been proposed. The operation of a number of prior systems depends upon receiving an indication of change in tire pressure within a vehicle tire. The indication of such changed tire pressure condition normally is given by a pressure-responsive switch. Various switches of the diaphragm, bellows or piston types have been used.
Also, some of such prior art switches have contemplated indicating a change in tire pressure either above or below certain predetermined ranges, as in Arvan U.S. Pat. No. 3,593,268.
Prior art switches for tire pressure signaling systems, including the device shown in U.S. Pat. No. 3,593,268, have had many undesirable features, characteristics or drawbacks, being high in cost, having a large number of delicate parts or components, using adjusting means to calibrate the switch for the predetermined tire pressure, and in the case of U.S. Pat. No. 3,593,268 having a contactor assembly comprising a large number of contactor parts including associated telescoping cups, one of which is movable from a first contact position to a second contact position and which is actuated by a push rod extending from a piston that is subjected to the internal tire pressure.
These difficulties or drawbacks, among others, and the relatively high cost of prior devices, seem to have delayed or retarded the adoption and desirable use of tire pressure signaling devices for automobile tires, and particularly of devices used to indicate change in tire pressure to one above or below the predetermined tire pressure desired to be maintained in the tire.
Thus, there has existed and still exists a need, particularly in the field of pleasure, business and commercial vehicles and the like, for air pressure-controlled electrical switches to indicate when tire pressure has been increased above or reduced below a predetermined level which it may be desired to be maintained in the tire so as to provide for highway operation of vehicles with security as regards tire pressure, at a minimum cost for the signaling systems.